So I just compiled the emulator for Win64 using MSYS 2 (which has a GCC 4.9.x), and the resulting Win64 has no sound. Internally, sound appears to be working, but I can hear nothing. No problems on the 32-bit compile.

Edit: Uncommented the pclog call in the error function in soundopenal.c and now the log is full of errors A004 which means invalid operation.

Edit #2: Found the reason. The code uses the DirectSound3D device, which however does not exist in Vista and later. PCem should instead enumerate devices and connect to the appropriate one.